Telephone-exchange system



E. R. SMITH 'TELEPHONE ExcHANGE SYSTEM ,way 17,1927. y 1,629,007

Filed A111411 9, 1925 roms y Affy.

- ent invention, the originating operator goes Patented lllay 17, 1.927.

UNITED STATES PATENT OFFICE.

ERMY R. SMITH, OF MAPLEWOOD, N JERSEY, ASSIGNOR, .'BY'MESNE ASSIGNMENTS,TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application lecl April 9, 1925., Serial No. 21,782.

y This invention relates to telephone systems and more particularly toimprovements in trunk circuits therefor used in the establishment ofconnections between' manual exchanges.

llhe invention is'adapted for use in sys-- tems in which calls `receivedat one exchange by a so-called A operator areextended by means of atrunk circuit to an operator of a dist-ant exchange commonly called a Boperator who thereupon completes the call to the desired subscriber. Insuch systems,V it is now usual for the A operator upon receiving` a callfrom a calling subscriber and ascertainingthe number desired, to employa call wire leading to the desired exchange to communicate with the Boperator. The B operator in responding, and after ascertaining thenumber desired. and the exchange at which the A operator is located,will assign a trunk to the A operator. The A operator then connects thecalling subscriber tosaid trunk, and the B operator extends the trunk tothe called subscribed. rEhis is known as the callwire system. Y

The present invention is designed to provide a ymeans. for connectingswitching trunks to an operatorstelephone set, such as that of a Boperator, so that traliic can be handled by the so-calledstraight-forward method of operation7V wherein no call-wire is employedand the circuit from calling` subscriber to called subscriber isprogressively established without the necessity of one operator askinganother which trunk she shall use. According to the presstraight forwardand chooses a trunk herself so that when the call is placed in the handsof the terminating or"B operator the connection has already beenestablished that far.

It is an object of the invention to provide a means whereby upon theselection of an idie trunk leading to a distant exchange b v an Aoperator. the B operator may manually connect such trunk to her set andat the sa if time automatically notify the A operator that she, the B7operator, is ready to receive the designation of the called line. Afterreceiving the number of the desired subscriber from the A operator, theB operator Will thereupon complete the call in the usual manner.

A feature ofthe invention comprises a means whereby 'a momentary tone istransmitted over the switching-trunk to the A operator when theB'operator connects such trunk to her set.

Another vfeature of the circuit arrangement is the provision of means toenable the B operator to completea connection to the subscribers linebyreinoving a plug from a lirst jack to which a call hadbeen extendedand inserting it into a second jack.

A further feature resides in an arrangementV for employing thisinvention in systems using the call circular method of operation so thata position using this straightforward method of trunking can also handletratlic of adjacent positions arranged for call circuit operation. Vhenthe operators set of a position employing the present invention isarranged for connection to a -oall circuit position, provision is madefor transmitting a signal to an operator at 'the' outward end of thecall circuit in case Another feature of the present inventionVV is theprovision of a plurailty of jacks lead- .ing tothe operators headset andthe provision of means associated therewith to render effective one ofsaid jacks at a time. By means of this feature the operator may insert asecond incoming trunk into one of' these jacks while she is stillcommunicating withan operator over a first trunk Aso that when sheremoves the plug of the first to complete a connection to a called linethe second Will immediately become effective. By the provision of thismeansV the service may be quiclened and delays due to the mechanicalhandling olf the apparatus reduced to a minimum.

One embodiment of the invention is illustrated in the acroinpairyingdrawing Which illustrates one form of the invention. In Fig. l, A showsa trunlf; leading from an outgoing exchange `which desires a connes.tion with an operator at the local exchange.

Only the portion of the 'l'riinl termin: yingat the local exchange isshown. l", illustrates a listening circuitto nhich the trunk circuit maybe connected. l-Tig. 2 represents a subscribers line jack. )nly thoseportions' of the circuit arrangement necessary to a proper understandingof the invention are shown.

A detailed description of the invention Will now be given. Assuming thatan A operator at an outgoing exchange desires to be connected to asubscriber at the exchange `wherein circuit B is located; she willtherefore connect to the calling subscriber in the usual manner andextend the connection by seizing a trunk leading to the desired e2;-change, in this instance, the exchange at Which circuit B is situated.Assuming that the jack into which the A operator plugs is thatassociated with trunk A, a signa Will be forwarded at the incomingexchang to light lamp l. The operation of lamp l effected as follows:grounded battery of relay 2, left-hand winding of relay 2, normalmake-before-break contact of relay 3, lower right-hand Winding ofrepeating coil Ll, through the loop at the calling, A operators end,back through the upper righthand Winding of repeating coil 1land theouter normal contacts of relay 8' to ground througl'i the right-handwinding of relay Relay 2 Will thereupon pull up its armature and causethe actuation of lamp l. in a circuit from grounded battery, filament oflamp l, normal right-hand contacts of relay 5, left-hand Winding ofrelay 3 to ground through the armature and alternate contacts of relay2. The operator at this exchange Will thus be apprise-:l that vthere isa call over trunk A associated With lamp l that awaits connection to asubscriber at this eX- change.

Relay 3 due to the energization of its lefthand Winding, Will attractits armature to break the normally closed contacts thereat and supply aground for relay 2. vrEhe lefthand Winding of relay 2 will nowoe-maintained energized by this ground. it is seen therefore thattheactuation of rel ay 8 causes the circuit leading to the A operator to bebroken.

rlhe operator at this end Will immediately take plug 6 of trunk Aassociated with lamp l and insert it into a listening jack such as 7 or8. .frssuming'that she plugs into jack S, a circuit will be closed fromgrounded battery through supervisory relay 9 of the trunk, lowerleft-hand Winding of repeating coil f-l through the ring ofthe `plug andjack, inner ieft-hand normal contacts of relay l() in the listeningcircuit, lower lefthand Winding of repeating coil ll, through theWinding of relay l@ lo ground. Supervisory relay 9 operates in thiscircuit and closes a circuit for the operation of relay as follows:Grounded battery, right-hand winding of relay 3 operated contacts andarmature of relay 9, left-hand winding of relay 3 to ground through theoperated contacts and armature of relay 2. Relay 3 therefore iscontrolled to maintain its armatures in a position that keeps open thecircuit leading to the A7 operator.. The reasons therefor ivill behereinafter set forth. Relay l2 operates and provides a ground forsleeve relay 5 in the trunk, which operates and causes theextinguishment of lamp l. The circuit therefore extends from groundedbattery, Winding of relayA 5, sleeve of the plug and jack respectively,Winding of relay 13, normally closed armature and conta cts of relay l0to ground through the righthand armature and contacts of relay l2 toground. Relay l2, by pulling up its lefthand armature ivill also close acircuit for relay la, through the normal make-beforebrealr contacts ofrelay l5.

it is of note therefore that sleeve relay 5 in the trunk circuit doesnot operate until after supervisory relay 9 has operated. This is forthe purpose of keeping relay 3 energized and preventingl the switchingtrunk from functioning to transmit a false signal to the A operator,upon the insertion of plugl G into jack S. if this feature were notprovided, and the signaling circuit to the A operator not broken, thelamp 35 or other means, at the A ope'ratoi"s position ivould be causedto operate upon the insertion of plug 6 into jack 8. rhis false signalwould erroneously be construed by the A operator to indicate that the Boperator had connected to the called subscriber; and hence the Aoperator would ring over the line. However, With this means. as aboveoutlined, no such false signal is flashed and hence the A operator Willnot ring. rThis prevents a so-called false plugged-up signal to the Aoperator. Of course, after the B oprator removes the trunk plug fron:jack S, and inserts it into the called subscriber-s jack 18, as Willhereinafter be disclosed, the A operator will then be signaled in theusual manner and will apply ringing current to the line.

It has been seen tha relay i3 operated in the circuit for relay 5. Taisis for the purpose of disconnecting the tip, ring and sleeve conductorsfrom jack T in order to prevent lll Cil

false operation in case the operator plugs anot-her switching trunk intothis jack before plug 6 is withdrawn from jack 8. i Relay 14 operatedafter the operation of relay 12 and by pulling up its inner lefthandarmature connects a tone to the line from source 16. Also it suppliesground for the operation of relay 15 through its righthand armature.Relay 15 in operating. will lock up to ground through the left-handarmature and contacts of relay 12 and will remain operated und-er thecontrol of said re.- lay 12. Relay 15 in locking to this relay willobviously cause a deenergization of relay 14. By making relay 14 slow torelease and relay 15 slow to operate the duration of the tonetransmitted back to the A operator may be accurately timed.

Upon the release of relay 14, relay 17 will operate in a circuit asfollows: Grounded battery, winding of relay 17, outer restored lett-handcontacts of relay ,14, armature and right-hand contacts of relay 15 toground.

Relay 14 in releasing will cut oii the toner from the line and relay 17which operates immediately thereafter will through the outer armaturesthereof now connect the operators telephone set to the line. Theoperaers jack 18 toxcomplete the connection.

Upon the withdrawal o plug 6 from jack 8, the supervisory relay willlose its holding lground and release. Supervisory yrelay 9 will alsorelease. Thiswill cause relay 3 to release and obviously closevv thecircuitfor the operation of the signal 35 at the A operatorsposition. Asthe plug 6 is inserted into jack 18 a circuit including sleeve relay andcut-oit relay 19 is closed and both these relays operate. As the loop ofthe called subscriber-s line is open at this time, the relay 9 does notoperate and hence lamp 1 remains dark and relay 3 does not operate asbefore. The A operator will then know that the trunk is plugged-up tothe called subscriber and will thereupon ring over the line.

Relay 14 is purposely made slow in releasing and relay is made slow inoperating, in order that the release of rthese relays will malte thecircuit- Afunction to transmit the momentary tone. described', overtheswitching trunk to the A operator. This tone indicates to the Aoperator that the switching trunk operator is being connected to thetrunk andready to receive the call. As has been seen, after she receivesdetails of the call, she withdraws Aplug 6 from the jack, releasingcircuit will'b'e connected to tone 16.

all the relays in the switching trunk; makes the usual busy test andcompletes the call.

When the called subscriber answers, supervisory relay 9 operates,whereupon relay 3 becomes operated. This operation cuts off battery andground from the distant Al operator and causes the extinguishment or'.lamp as a signal that the subscriber has answered. Relay 3 also locks inrelay 2 and hence the lamp 1 remains dark until the called subscriberhangs up. Vhen this happens relay 9 returns to normal and releases relay3, whereupon relay 2 is again connected to the distant A operator andlamp 35 is lighted as a signalthat the conversation has ended. The Aoperator then opens the loop at her end of the trunk and relay 2releases, whereupon lamp 1 becomes lighted in a circuit including theback contact of relay 2 and the front contact of relay 5. This is vasignal to the B operator to remove plug 6 trated in the drawing, theleads of the-call circuitsvshown are normally connected to an operatorstelephone set, through the -contacts of relay'17. lIt is evidenttherefore that if the operatoris busy answering a call with thelistening jack circuit, relay 17 .will be operated and the operators setdisconnected from the call circuit leads. Instead, the clall T iis tonenotities the operator at the outward end of the called circuit that theinwardoperator'is'not'y yet free-to answer the call. VObviously, afterrelay 17 restores, the call circuit leads will` again be 'connected toIthe opera tors set and disconnected from the tone.

The call circuit operator will theny passv the call inthe usual manner.It is evident that any number of call circuits and any number oflistening jack circuits may bemultipled together, but for purposes ofthis invention, only one set of call circuit leads and two listeningacks are shown.

If jack 7 were used instead of jack 8, in the operation set. forth,relay 10 would function in a similar manner does relay 13 and in placethereof. Thus, if jack 7v were seized and a second switching trunkassociated therewith, before a irst trunk in jack S was removed, relay13 would prevent the connection of the tip, ring', andsleeve conductorsto jack 7, and hence assure the seizure of the listening circuit by only.one trunk at a time. Upon the removal of' the first trunk from jack Y8,the second trunk, in jack 7, would, as has been described, be connectedto the listening circuit, and relay l()y operate to prevent falseoperation upon the possible seizure ot the other jack, and so on.

lt should turther he noted that relays 1'() and 13 are slow to release,so that il there a plug irrboth jacks 7 and and the one in jack 8 isellective, 'relay lf3 willihe operated 'and when the plug in jack tu isremoved, relay 13 being" slow to release its armatures will give rel-ay12 time to become:deenergized. Thereupon relay l5 will return to normal,so that upon the/complete release ol relay l?) and the sul-)sequentcnercization olf relay '12, the tone current from source 1G will hemomentarily applied tothe 'truuk now connectedthrough jack 7.

It is seen, theretore,that only one oli the jacks is etlfective at atime. even though a second ack is seized while a lirst is stillihusy. l"he operator may, as a result, handle the apparatus toits ful-l capacity,luy answering' and completing calls practically contemporaneously due`to a lplurality ot jacks 'being available to her, without- Ytear olrcausing," confused or false operation.

Vfhat claimedis: Y

l. ln a telephone system, a trunk circuit, an independent circuithaving;` listening means associa-ted therewith and adapted to heconnected to said' trunk, a source ottone current, land means responsiveto the conneet-ionl ol said trunk circuit yto said'y independent circuitto automatically and'sequentially connect said source ot tonecurrent tosaid trunk, to disconnectI said source of vtone current from said trunkand to connect said listening apparatus to said truuk.

2. In a telephone system, a first trunk ot a certain character, asecond^trunk ot' a dii-ferent character', an operators'headset normallyconnected to said first trunk, means for 'connecting said headset tosaid 'second' trunk, a source ot tone current, and means tor connectingsaid source of 4tone current to said iirst ltrunkupon the disconnectiontherefrom` of sa-id headset and the connection ot' said headset to theother trunk.

ln a telephone system, a trunk ot a certain character, an operatorstelephone set normally connected to said trunk,trunks ot othercharacter, means for connecting said headset to said other trunks, asource of tone current, and means for connectingY said source of tonecurrent to said trunk of a certain character, upon the disconnect-ionot' said telephone set therefrom. v

4. In a. telephone system, a plurality of trunk circuits, anindependent-circuit having listening means associated therewith andadapted to be cminectedto any ot said trunks, means for associatingvmore than one of said trunks with said independent circuit at one time,means for rendering` etfective only one such connection at a time, meansfor automatically'rendering effective another such connection upon thebreaking of a previously effective connection, a source of tone current,and means responsive to the eil'ectivc connection of one ot said trunkcircuits with said independent circuit' lor automatically andsequentially connecting said source ot tone current to said trunk,disconnectingj said source et tone current from said trunk andlconnecting` said listening, apparat-us to said trunk.

ln a telephone system, a plurality oil" lrun c circuits terniinating inplugs, a plurality ot jacks, a telephone headset associated with saidjacks, means for successively associatingsaid trunks with said jacks,means responsive thereto for successively associatingsaid telephone setto said trunks, said set being automatically connect-- ed to only one ofsaid trunks at one time in the order o' their connection to said jacks,a source of tone current, and means responsive to said' second mentionedmeans tor momentarily connecting,` said source ot tone current lto saidtrunks.

(i. ln al telephone system, a call wire circuit. a trunk circuit, anindependent circuit having listening vapparat-us associated therewith,means operative responsive to the interconnection of' said trunk circuitwith said independent circuit to connect the listening apparatusthereto, a source of tone current, and 'means responsive to saidinterconnect-ion tor connecting` said source ot tone current to the saidcall Wire circuit. v

` T. In a telephone system, a. irst trunk, a second trunk, anindependent circuit adapted to he connected to said trunks and havingilistening apparatus associated therewith, a characteristic signaling'means, means responsive to the connection of said circuitwith one Otsaid trunks'to momentarily associate said signaling means therewith,means operative responsive thereto 'lor connecting said listeningapparatus to saidV trunk and transferringthe connection ot saidsignaling means to the other of said trunks. A

8. In a telephone system, a plurality of telephone exchanges, anexchange X, trunk lines of a certain character leading from some ot'said telephone exchanges to e3:- changes X, trunk lines ot a dilterentcharacter leading` from other ot' said exchanges to exchange X,listening apparatus at said exchange X, said listening apparatus beingnormally connected to trunks of a certain character and means responsivet-o the connection of said telephone equipment to trunks -ot anothercharacter for disconnecting,` said listening apparatus from the trunksnormally connected thereto.

'9. In-'a telephone system, a trunk terminating in a plug, listeningapparatus associated with a jack, a subscribers line terminating inanother jack, a signal, means responsive to the connection of said trunkwith ter relay in said independent circuit, a vsecthe first ot saidjacks for connecting said listening` apparatus to said trunk andmaintaining said signal in a certain condition, and means responsive tothe connection of said trunlr With the ot-her of said acks for changingthe condition of said signal.

10. In a telephone system, a trunk lin terminating in a plug, listeningapparatus associated with a jack, a subscribers line terminating inanother jack, aA signal, means responsive to the connection ot saidtrunk with t-he first of said aclrs for connecting said listeningapparatus to said trunk, and means responsive to the connection of saidtrunk with the other of said jacks for disconnecting said listeningapparatus from said trunk and for actuating said signal.

11. In a telephone system, a trunk circuit terminating in aY plug, arelay in said trunkv circuit for controlling a signal therein, anothercircuit terminating in a jack, a master relay in said other circuit, asubscribers line terminating in a jack, a means responsive to theconnection of said trunk with said other circuit, under the control ofsaid 1nasterre lay, for operating said relay in the trunk circuit andmaintaining the signal therein in a desired condition, and meansresponsive to the disconnection of said trunk from said other circuitand its connection to said subscribers line for causing the restorationof said relays and a change in the condition of said sional.

12. n a telephone trunking system, a trunk terminating in a plug,tele-phone listening apparatus associated With an independent circuitterminating in a jack, a masond relay under the control of said masterrelay and a third relay, means operative responsive to theinterconnection of said trunk and independent circuit for causing saidmaster relay to operate and effect the actuation of said second relay,means responsive to the actuation of said second relay to cause theoperation of said third relay and the release of said second relay, afourth relay, and means under the control of said second and thirdrelays for causing a momentary tone to be connected to said trunk andfor causing the immediate connection of said listening apparatus to theinterconnected circuits under control of said fourth relay, said tonebeing disconnected from the trunk upon the connection of the listeningapparatus thereto. 13. In a telephone system, a plurality of trunkcircuits terminating in plugs, an independent circuit having a pluralityof acks associated therewith, listening apparatus associated with saidindependent circuit, means responsive to the interconnection of aplurality of trunks with said circuit by the respective connection ofthe plugs thereof with said jacks for connecting said listeningapparat-us With one of said trunks, and for connecting said listeningapparatus to a second of said trunks upon the removal of the plug of thefirst trunk from a jack of said circuit, a source of tone current,and'means responsive to said first mentioned means for momentarilyconnecting` said source of tone current to said trunks. l

` In Witness whereof, I hereunto subscribe my name this 8 day of AprilA. D., 1925.

ERMY R. SMITH.

